According to medical professor Joel D. Howell, OMT is based on the idea that a myofascial continuity "links every part of the body with every other part"; a practitioner, through a "skillful and dexterous use of the hands" treats what was originally called "the osteopathic lesion", but which is now named "somatic dysfunction".[1] The most commonly treated ailment is back pain, although some practitioners claim OMT can be used to treat a wide range of conditions.[2] It has been proposed as effective for treating a number of diseases including asthma, pancreatitis, and Parkinson's disease.[1]

Andrew Taylor Still, M.D., D.O. was a 19th-century American physician and Civil War surgeon who founded osteopathic medicine. Following the loss of three of his children to spinal meningitis, Still became dissatisfied with contemporary medical practices and sought to further medical understanding and treatment.[3] Still claimed that human illness was rooted in problems with the musculoskeletal system, and that hands-on manipulations could solve these problems and so effect a cure by harnessing the body's own self-repairing potential.[4] Still's proposed treatment regime also included as strong dose of healthy living: he advocated abstinence from alcohol, and patients were forbidden from taking medicine.[1]

One key concept osteopathic medical students learn is that structure influences function. Thus, if there is a problem in one part of the body’s structure, function in that area, and possibly in other areas, may be affected. Another integral tenet of osteopathic medicine is the body’s innate ability to heal itself. Many of osteopathic medicine’s manipulative techniques are aimed at reducing or eliminating the impediments to proper structure and function so the self-healing mechanism can assume its role in restoring a person to health.[6]

Osteopathic medicine defines a concept of health care that embraces the concept of the unity of the living organism's structure (anatomy) and function (physiology). The American Osteopathic Association (AOA) state that the four major principles of osteopathic medicine are the following:[7]

Muscle energy techniques address somatic dysfunction through stretching and muscle contraction. For example, if a person is unable to fully abduct her arm, the treating physician raises the patient's arm near the end of the patient's range of motion, also called the edge of the restrictive barrier. The patient then tries to lower her arm, while the physician provides resistance. This resistance against the patient's motion allows for isometric contraction of the patient's muscle. Once the patient relaxes, her range of motion increases slightly. The repetition of alternating cycles of contraction and subsequent relaxation help the treated muscle improve its range of motion.[8] Muscle energy techniques are contraindicated in patients with fractures, crush injuries, dislocations, joint instability, severe muscle spasms or strains, severe osteoporosis, severe whiplash injury, vertebrobasilar insufficiency, severe illness, and recent surgery.

Counterstrain is a system of diagnosis and treatment that considers the physical dysfunction to be a continuing, inappropriate strain reflex, which is inhibited during treatment by applying a position of mild strain in the direction exactly opposite to that of the reflex.[9] After a counterstrain point tender to palpation has been diagnosed,[10] the identified tender point is treated by the osteopathic physician who, while monitoring the tender point, positions the patient such that the point is no longer tender to palpation.[11] This position is held for ninety seconds and the patient is subsequently returned to her normal posture.[10] Most often this position of ease is usually achieved by shortening the muscle of interest.[11] Improvement or resolution of the tenderness at the identified counterstrain point is the desired outcome.[10] The use of counterstrain technique is contraindicated in patients with severe osteoporosis, pathology of the vertebral arteries, and in patients who are very ill or cannot voluntarily relax during the procedure.

Myofascial release is a form of soft tissue therapy used to treat somatic dysfunction and the resultant pain and restriction of motion. Treatment requires continual palpatory feedback to achieve release of myofascial tissues.[12] This is accomplished by relaxing contracted muscles, increasing circulation and lymphatic drainage, and stimulating the stretch reflex of muscles and overlying fascia.[15]

Fascia is the soft tissue component of the connective tissue that provides support and protection for most structures within the human body, including muscle. This soft tissue can become restricted due to psychogenic disease, overuse, trauma, infectious agents, or inactivity, often resulting in pain, muscle tension, and corresponding diminished blood flow.[16] Although fascia and its corresponding muscle are the main targets of myofascial release, other tissue may be affected as well, including other connective tissue.[15]

Lymphatic pump treatment (LPT) is a manual technique intended to encourage lymph flow in a person's lymphatic system.[citation needed] The technique can be applied to the thoracic cage, abdomen, pelvic diaphragm, legs, and over the spleen and the liver.[17] The first modern lymphatic pump technique was developed in 1920, although osteopathic physicians used various forms of lymphatic techniques as early as the late 19th century.[18]

In dogs and rats, lymphatic pump treatment techniques have been found increase lymph flow.[17] Research has demonstrated the technique produces a strong, short-term increase in the flow of lymphatic fluid, and stimulate the mobilization of immune cells in the lymphoid tissue of the gastrointestinal tract, from both the mesenteric lymph nodes and gut-associated lymphoid tissue; preliminary research in humans suggests that lymphatic pump techniques may be able to improve the immune response to vaccinations.[17] Relative contraindications for the use of lymphatic pump treatments include fractures, abscesses or localized infections, and severe bacterial infections with body temperature elevated higher than 102 °F (39 °C).[19]

In 2013, a Cochrane Review reviewed six randomized controlled trials which investigated the effect of four types of chest physiotherapy (including OMT) as adjunctive treatments for pneumonia in adults and concluded that "based on current limited evidence, chest physiotherapy might not be recommended as routine additional treatment for pneumonia in adults."[21] A 2013 systematic review of the use of OMT for treating pediatric conditions concluded that its effectiveness was unproven.[22]

In 2011, a systematic review found no compelling evidence that osteopathic manipulation was effective for the treatment of musculoskeletal pain.[23] A 2013 systematic review found insufficient evidence to rate osteopathic manipulation for chronic nonspecific low back pain.[24]

Initially, D.O.s were regarded by M.D.s as "cultists" whose treatments were rooted in "pseudoscientific dogma", and tensions between the two continued for many years.[4]

In 1988, Petr Skrabanek classified osteopathy as one of the "paranormal" forms of alternative medicine, commenting that it has a view of disease which had no meaning outside its own closed system.[26]

In a 1995 conference address the president of the Association of American Medical Colleges, Jordan J. Cohen, pinpointed OMT as a defining difference between M.D.s and D.O.s; while he saw there was no quarrel in the appropriateness of manipulation for musculoskeletal treatment, the difficulty centered on "applying manipulative therapy to treat other systemic diseases" – at that point, Cohen maintained, "we enter the realm of skepticism on the part of the allopathic world."[4]

In 1998 Stephen Barrett of Quackwatch posted a highly critical article online entitled "Dubious Osteopathic Practices", in which he said that the worth of manipulative therapy had been exaggerated and that the American Osteopathic Association (AOA) was acting unethically by failing to condemn craniosacral therapy. The article attracted a letter from the law firm representing the AOA accusing Barrett of libel and demanding an apology to avert legal action.[4] In response Barrett made some slight modifications to his text, while maintaining its overall stance; he queried the AOA's reference to "the body's natural tendency toward good health" and challenged them to "provide [him] with adequate scientific evidence showing how this belief has been tested and demonstrated to be true."[4] Barrett has been quoted as saying "the pseudoscience within osteopathy can't compete with the science".[4]

In 1999, Joel D. Howell noted that osteopathy and medicine as practiced by M.D.s were becoming increasingly convergent. He suggested that this raised a paradox:

if osteopathy has become the functional equivalent of allopathy, what is the justification for its continued existence? And if there is value in therapy that is uniquely osteopathic – that is, based on osteopathic manipulation or other techniques – why should its use be limited to osteopaths?[1]

In 2004, the osteopathic physician Bryan E. Bledsoe, a professor of emergency medicine, wrote disparagingly of the "pseudoscience" at the foundation of OMT. In his view, "OMT will and should follow homeopathy, magnetic healing, chiropractic, and other outdated practices into the pages of medical history".[27]

In 2010, Steven Salzberg wrote that OMT was promoted as a special distinguishing element of DO training, but that it amounted to no more than "'extra' training in pseudoscientific practices".[28]